Technical Field
The present disclosure generally relates to measurement of parameters in multi-phase electrical systems.
Description of the Related Art
Although single-phase electrical systems may be used to supply electricity to domestic and commercial electrical appliances, three-phase alternating current (AC) electrical systems are commonly used to distribute electrical power and to supply electrical power to power equipment rated for relatively high power.
FIG. 1 shows an example three-phase electrical system 10 that includes a three-phase source 12 electrically coupled to a three-phase load 14. In this particular example, the three-phase source 12 includes four conductors, labeled A, B, C, and N, coupled to the three-phase load 14. The conductors A, B, and C each carry AC voltages of identical frequency and similar magnitude, and the conductor N is a common return. The phase of each of the AC voltages in the conductors A, B, and C is separated by 120° from each other. For example, the phase of the voltage in the conductor A may be 0°, the phase of the voltage in the conductor B may be +120°, and the phase of the voltage in the conductor C may be +240°. The three-phase electrical system 10 may be arranged in a delta (Δ) configuration, wye (Y) configuration, etc.
Electrical parameters may be measured in single-phase electrical systems using a wattmeter. Examples of such electrical parameters may include active power, apparent power, volt-amperes reactive power, power factor, harmonics, current, voltage, phase shift, etc. However, measurement of electrical parameters for multi-phase electrical systems is more difficult. As shown in FIG. 1, three voltage measurement channels VCH1, VCH2, and VCH3 and three current measurement channels ACH1, ACH2, and ACH3 are used to measure the electrical parameters of the three-phase electrical system. Each of the voltage/current channel pairs (e.g., VCH1/ACH1) may be associated with a separate wattmeter (i.e., three wattmeters total), or all of the channels may be part of a single multi-channel wattmeter.
The setup of such a three-phase measurement may take a significant amount of time and effort for a technician. This is especially the case for electrical systems that are positioned in tight spaces with restricted access, and for electrical systems that have unlabeled conductors. In practice, the technician has to connect four voltage leads, one for each of the conductors A, B, C, and N, to the electrical system, and also has to connect at least three current sensors in series on the correct voltage lines. Thus, a minimum of seven test leads are required to be connected before a measurement can be obtained.